Electron multiplier



Feb. 18, 1958 s. G. FONG EI'AL 2,824,253

ELECTRON MULTIPLIER 2 Shaets -Sheet, 1

Filed Nov. 24, 1953 INVENTORS. SAMUEL G. FONG By HANS W. G. SAL/NGER ,M,J;/M z/M ATTOkNEYS Feb. 18, 1958 s. G. FONG ETAL 2,824,253

ELECTRON MULTIPLIER 2 Sheets-Sheet 2 Filed Nov. 24, 1953 'ilmumnl 5 7 2 .lnmmm INVENTORS. SAMUEL G. FONG HANS W G. SAL/NGER v m T BY M JzziflM 1M ATTORNEYS United States Patent 2,824,253 ELECTRON MULTIPLIER Samuel G. Fong and Hans W. G. Salinger, Fort Wayne,

Ind., asslgnors to International Telephone and Telegraph Corporation 7 Application November 24, 1953, Serial No. 394,124

7 Claims. 01. 313-105 This invention relates to electron multipliers and more particularly to an improved electrode structure for a multi-stage electron multiplier tube of the static type.

A static multi-stage electron multiplier tube generally comprises a series of secondary emissive electrodes, each successive electrode being provided with a progressively higher positive potential. These electrodes are placed in secondary-emissive relation with each other so that a primary beam of electrons issuing from a source may be directed from electrode to electrode and thence finally to a collector electrode to which is applied the highest positive potential. The action of the tube is such that an initial beam of electrons from, for example, a cathode, strikes the first electrode which liberates secondary electrons. The secondary electrons augment the electron beam and are given additional velocity by the adjacent, succeeding electrode. The augmented beam is caused to impinge on this adjacent electrode with suflicient force to liberate additional secondary electrons. Thus, each electrode may be considered as an electron multiplier, since it introduces additional electrons of a ratio greater than unity into the stream. The augmented electron stream is eventually collected by a collector, or output electrode, to which is applied the highest positive electric potential.

Known types of multi-stage multiplier tubes are relatively bulky in size due to the necessity of positioning the several secondary emitting electrodes in secondary emissive relation with each other. These known types have assumed linear configurations wherein two parallel opposite rows of cylindrical electrodes are provided, the electrodes of the two respective rows being longitudinally staggered with respect to each other and arranged to direct electron flow across the rows between longitudinally adjacent electrodes. It is also known to dispose the two rows of electrodes in two concentric circles to reduce the physical size of the tube. In all known prior art devices, the directing of the electron stream occurs between electrodes in common parallel planes. Our invention comprises a multi-stage multiplier tube having a source of secondary-emissive electrodes characterized by the fact that adjacent electrodes provide an electron path therebetween, successive paths extending at right angles to each other thereby lying in a common plane, successive pairs of said paths defining alternate planes which are normal to each other and symmetrically related about a common axis. This enables the construction of a multistage multiplier tube of smaller size than heretofore obtainable.

Accordingly, the object of our invention is to provide a simple, improved multi-stage electron multiplier tube of the static type having a small physical size.

A still further object of the invention is to provide an improve multi-stage electron multiplier tube wherein the electron stream is deflected twice in the same plane.

Other objects and advantages of the present invention willbeco'me apparent from the following detailed descriptior'i-of a preferred form of our novel electrode structure 2 taken in connection with the accompanying drawing in which: v

Fig. l is a perspective schematic view ofour improved electrode structure in amulti-stage electron multiplier tube; and

Fig. 2 is a schematic diagram of the planes of the electron paths within the tube; p p p p In the drawing, all the elements are diagrammatically shown, each being well understood by those skilled in the art.

Referring now to Fig. 1, there is shown a tube envelope 1 in which a source of electrons is diagrammatically shown at 2. A plurality of electrodes or dynodes 4 14 are arranged in series and in various planes between the source 2 and a collector electrode 3. The dynodes may be of any desired shape or configuration, so long as each is in secondary-emissive relation with the adjacent dynode in the series, and the path of the electrons emitted from source 2 is directed to dynode 4 and thence to succeeding dynodes 5-14 and, ultimately, to collector 3. In a preferred embodiment, we used substantially box-shaped dynodes, each having two adjacent sides open and having the opposite adjacent sides joined by a rounded surface. The rounded corners of the dynodes are indicated by reference numerals 4a 14a, respectively. These particular dynodes are already known to those skilled in the are and are shown, for instance, in U. S. Patent No. 2,585,044, issued to R. W. Sanders.

To return to the description of Fig. 1 hereof, the several respective dynodes 4 14 are aligned in secondary-emissive relation with the adjacent dynodes in the series. Secondary-emissive relation is achieved by disposing the open sides of each of the respective dynodes in registry with the open side of the adjacent dynode. Thus, open side 4b of dynode 4 is in registry with the electron source 3, and its open side 40 is in registry with the open side 5b of dynode 5. In turn, dynode 5 is positioned so that its open side 50 is in registry with open side 6b of dynode 6. Thus, it will be seen that a stream of electrons emanating from source 2 will successively strike curved surfaces 4a, 5a and 6a of dynodes 4, 5 and 6 respectively. As explained thus far, the deflected beam will travel from dynode 4 to dynode 6 in a common horizontal plane. Dynode 6 is arranged so that its open side 60 is in registry with the open side 7b of dynode 7. It will now be apparent that the electron beam will now travel in a vertical plane or normal to the path of travel it theretofore described among dynodes 4, 5 and 6. It will be observed that the path of the electron stream from dynode 4 to dynode 5, is normal to the path of the stream from dynode 5 to dynode 6 although both paths are in a common horizontal plane. The path of the electron stream continues from dynode to dynode, i. e., from dynode 7 through the remaining dynodes 8 13 and to dynode 14 in identical fashion, and ultimately leads to collector electrode 3 which is in registry with open side 14c.

It will be appreciated that the dynode structure is so arranged that alternate electron paths are symmetrical about a common axis which is in the center of the tube and which is indicated by the dashed line y-y. This axial placement enables the dynode structure to be compactly arranged within a comparatively small tube envelope.

On the input side of each dynode, we provide the customary grid gratings, indicated as 4d 14d. For

clarity and convenience of illustration, only the grid gratings 4d, 5d, 7d, 9d, 10d, 11d and 13d are shown; the input sides of dynodes 6, 8, 12 and 14 being in planes not visible in the perspective view. It will be also appreciated that each dynode, each grid grating, the electron source and the collector electrode is provided with a separate support (not shown) to maintain the several elements Patented Feb. 18, 1958 r 3 in their proper position within the tube envelope, as well as to furnish separate electrical connections (not shown) to the exterior of the tube.

In Fig. 2, there is schematically shown horizontal planes 15 18 which will aid in understanding how successive electron paths are normal to each other and how successive pairs of paths lie in respective planes at right angles to each other, all of said paths describing a symmetrical revolution about a common axis yy' which may traverse planes 1518 at right angles thereto.

In operation, electrons emitted from source 2 are attracted through the grid grating 4d to the inside curved surface 4a of dynode 4 which, as explained in the foregoing, liberates secondary electrons at a ratio greater than unity for each primary electron. The secondary electrons liberated from dynode 4 are directed through the grid 5d of dynode 5 and similarly, secondary electrons are liberated from the inside curved surface 57. The same operation occurs successively with dynodes 6 14 respectively, each dynode liberating secondary electrons having a greater velocity than those liberated from the preceding dynode due to the fact that each dynode is connected to a progressively higher potential as taught in Sanders patent mentioned earlier. Thus, the electron paths from dynodes 4-56 are in a common horizontal plane although at right angles to each other. The path from dynode 6 to dynode 7 lies in a vertical plane. The paths from dynodes 7-89 are again in a common horizontal plane but at right angles to each other. This relationship progresses through to the last dynode 14. It will now be apparent that by reason of the novel construction of our device, the electron stream may be deflected twice in the same plane and by virtually revolving the respective paths about a common axis, maximum use is made of a given envelope space.

While the principles of the invention have been described above in connection with a specific embodiment, it is to be clearly understood that this description is'made only by way of example and not as a limitation as to the scope of the invention which is defined by the appended claims.

What is claimed is:

l. A multi-stage electron multiplier tube comprising a series of at least four spaced, secondary-emissive electrodes, three of said electrodes being spaced apart horizontally, the fourth electrode being spaced vertically from said three electrodes and in electron-receiving registry with one of said three electrodes, all of said electrodes including means for defining successive electron beam paths therebetween.

' 2. A multi-stage electron multiplier tube comprising a series of spaced electrodes, said electrodes being secondary emissive, said electrodes being arranged in groups of three with different groups being spaced apart, said groups being aligned in respective parallel planes and being in electron-passing registry with each other, the three electrodes of each group being disposed in electronpassing relation with each other and symmetrically arranged about a common axis, said electrodes including means for defining successive electron beam paths therebetween.

3. A multi-stage electron multiplier tube comprising an electron collector and a series of at least four spaced, secondary-emissive electrodes within said tube, the first of said electrodes being exposed to impinging primary electrons, the other electrodes being disposed between said first electrode and said collector, the first, second and third electrodes being aligned in a single plane in electronpassing relation, the fourth and collector electrodes being aligned in a second plane parallel to said single plane, the fourth electrode being disposed in electron-receiving registry with said third electrode, all of said electrodes including means for defining successive electron beam paths therebetween.

A multistage electron multiplier tube as claimed in claim 3, wherein said electrodes are box-shaped, each electrode having two open sides and two closed sides, the closed sides being joined by a rounded corner provided with a secondary-emissive surface, the open sides of each electrode being in registry with the respective open sides of the two adjacent electrodes.

5. A multi-stage electron multiplier as claimed in claim 1 wherein said electrodes are box-shaped, said electrode having two open sides and two closed sides, the closed sides being joined by a rounded corner provided with a secondary-emissive surface, the open sides of each electrode being in registry with the respective open sides of the two adjacent electrodes, the axes of the rounded surfaces of adjacent electrodes being spaced apart in normal relation to each other.

6. A-multi-stage electron multiplier tube comprising a plurality of spaced, secondary-emissive electrodes, said electrodes being arranged in groups of three with each group being aligned in a respective plane, the planes of each group being spaced apart and parallel, all of said electrodes being symmetrically arranged about a common tube axis, said electrodes being box-shaped having two closed sides and two open sides, the closed sides being joined by a rounded corner provided with a secondary-emissivc surface, the open sides of each electrode being in registry withthe respective open sides of the two adjacent electrodes, the axes of the rounded surfaces of adjacent electrodes being spaced apart in normal relation to each other.

7. A multi-stage electron multiplier tube comprising a plurality of spaced, secondary-emissive electrodes, said electrodes being arranged in groups of three with each group being aligned in a respective plane, the planes of each group being spaced apart and parallel, all of said electrodes being symmetrically arranged about a common tube axis, said electrodes being box-shaped having two closed sides and two open sides, the closed sides being joined by a rounded corner provided with a secondaryemissive surface, the open sides of each electrode being in registry with the respective open sides of the two adjacent electrodes, the axes of the rounded surfaces of adjacent electrodes being spaced apart in normal relation to each other, and a grid covering that open side of each electrode facing the preceding electrode.

References Cited in the file of this patent UNITED STATES PATENTS 2,163,966 Snyder June 27, 1939 2,245,614 Shockley June 17, 1941 FOREIGN PATENTS 881,199 France Ian. 15, 1943 

